1. Field of the Invention
The present invention is directed generally to planar optical displays and, more particularly, to a method of creating uniform adhesive layers in a planar optical display and a method of producing a black cladding layer having small particulate size for use in a planar optical display.
2. Description of the Background
The television, computer, and display industries are moving toward flat screens to provide pictures for entertainment, scientific, and job related activities. Planar optical displays (POD) provide pictures without the use of a picture tube, thereby allowing for flatter display screens than picture tube displays. However, planar optical displays use a black cladding layer between optical panel waveguide layers, and the cladding layer can provide limitations on screen size and resolution.
For example, uneven thickness of the cladding layer at the optical input face to the POD makes it difficult to couple the light from a rectangular image source into the POD if the POD input face is not perfectly rectangular. Variations in the thickness of the cladding layer are primarily due to variations in the particle size of the black pigment used to create the black cladding layer. In fact, a typical display screen having a thickness of 2 inches might have 0.030xe2x80x3 to 0.040xe2x80x3 thickness variation across its width.
Additionally, bubbles may sometimes appear in the finished output face of the POD. A bubble may show as a light spot in the output picture, or an area of reduced contrast in the output picture. Thus, such bubbles are a visible annoyance to the viewer, and are difficult to overcome, even by adding filtering layers between the viewer and the bubbles.
Finally, variability in the particle size of the black pigment particles used in the cladding layers leads to picture non-uniformities. Where carbon black or bone charcoal particles are used, the particle size can vary from 5 microns to approximately 50 microns, with an average particle size of about 40 microns. Particles of finer sizes, as small as 0.05 microns, clump together into larger particles having sizes of 5 to 10 microns when taken out of the solution into which those particles were pulverized.
Therefore, the need exists for a planar optical display that has a uniformity in the thickness of the black cladding layer, and that has a smaller particle size of the particles in the black cladding layer, while eliminating bubbles from the black cladding layer.
The present invention is directed to a method of creating uniform adhesive layers in a planar optical display. The method includes providing an adhesive reservoir, providing at least two optical panels, placing spacers between the top edges of the optical panels and the bottom edges of the optical panels, or between the left and right sides of the optical panels, thereby forming a stack of optical panels having at least one uniform gap between adjacent ones of the optical panels, placing the stack into a panel reservoir having a height and a width, which panel reservoir is connected to the adhesive reservoir by a fluid path, and injecting adhesive from the adhesive reservoir through the fluid path into the bottom of the panel reservoir until each uniform gap is filled.
The present invention also includes a method of producing a black cladding layer having small particulate size for use in a planar optical display. The method includes providing black pigment having a fine particulate size of approximately 0.05 microns, placing the particulates in solution, filtering the epoxy having the fine black particles in solution, stacking a plurality of optical panels in a fixture in the presence of the filtered epoxy, and curing the stack.
The present invention solves problems experienced with the prior art because the variability in the uniformity due to bubbles and clumped particles of the black cladding layer is decreased by a factor of 20 through the use of the methods of the present invention, smaller particle sizes increase screen uniformity and allow for greater flatness of the POD, and the use of less black pigment, by weight, made possible by the present invention increase the optical efficiency of the POD. These and other advantages and benefits of the present invention will become apparent from the detailed description of the invention hereinbelow.